you still pay for a license
Sorry, I didn't get what your point is, could you elucidate it? Because even for a physical medium, which can be held on hands, the user is still paying for a "license" (i.e. the license to use the software/game). Even for free (free as in free beer) games, the user is still receiving a "license", even though it's a gratis license.
but if you don’t own it why pay for it?
I'll use Terraria as an example for the following statement. The only way to "own" Terraria would be either owning or being Re-logic, the company behind Terraria. Even if Terraria was distributed through CD/DVD, the gamer owns just a copy, the copy that's written within the medium.
why pay for it?
It's worth mentioning that GoG has both free and paid games. For example, "Endless sky" is free, anyone can get it there without costs.
As for paid games, why pay for it? Well, it's a good question, why pay for a game? I guess the answer tends to be subjective and strictly personal to everybody that answers it. I paid for Terraria because it's a nice game to me. I paid for Slime Rancher, Kerbal Space Program, BeamNG Drive, among other games, because they're nice simulation/open-world games to me. Not everybody thinks these games are nice. I wouldn't pay for games such as Football Manager, DayZ, RDD, because I wouldn't play them, because they aren't the game genres I'd like. Therefore, I particularly pay for a game and play it when I really like the game.
